The game should automatically prompt you (in the right hand bar) when a colony ship reaches a habitable system.

It did do that, but then it stopped doing so. I send colony ships to a planet I'm able to colonize and it just sits there. I've even tried moving the ship to a different system and then back to the target one. Nada.

Is there a limit of how many colonies I can have? Do I need some sort of tech or other requirement to have more than 5 or 6 colonies?

Do you have alot of other ships at the planet your trying to colonize? If so try moving them away and your colony ship away and come back to the planet with just the colony ship.

sounds like he's using a colony ship that doesnt have the proper colony module, like, trying to colonize an inferno planet without an inferno colony module.

To quickly see planets that you have the tech to colonize, click "Map". There should be options to help you.

It's not enough to have the tech to colonize a tundra world in general - you need to build a colony ship with the tundra colony module installed. Just knowing how to set up a colony on a really cold world won't help your colonists unless you make sure to pack their long underwear and industrial strength space heaters.

I think maybe this is it. While you may have researched the technology, it isn't automatically implemented on your subsequent colony ships - you need to use the ship design screen to create a new colony ship design with the Tundra colony module (or use a higher tech version, such as radiated or inferno), and then build that new type. Naturally, the higher-tech colony modules require more space and cost more...

Err, credit to rakenan, too.

Ah, ok. Sure, that makes total sense. I was just assuming it would automatically work. Thanks for the help!